Chelsea are reluctant to sell Juan Mata to a Premier League rival while the fallout from their failed attempt to sign Wayne Rooney in the summer is another major obstacle to the midfielder joining Manchester United.

Mata has been on the fringes of the team under Jose Mourinho this season and has not played since his angry reaction to being substituted at Southampton on New Year’s Day.

The 25-year-old is not happy and needs regular football to cement a place in Spain’s World Cup squad but there are complications to a January move.

United are interested but Chelsea would prefer to sell abroad if Mata pressed for a transfer. The London club are also conscious it would be a gamble losing him as an injury to Oscar, Willian or Eden Hazard would leave them short in the attacking midfield role.

It is difficult to see a motive for Chelsea to sell — and thus give United manager David Moyes a potential lifeline — unless such a deal is contingent on Rooney heading to Stamford Bridge.

But United consider last summer’s dispute with Mourinho over Rooney to be a major impediment to an attempt to sign Mata and do not intend to sell the striker as part of any deal.

United have indicated only that they have not yet bid for Mata — leaving open the prospect of a move in the next 48 hours — but there is no optimism at Old Trafford that they can persuade the Blues to do a straight cash deal.

United will not sell Rooney as he is considered a key part of the rebuilding job at Old Trafford — especially if Moyes’s side slip out of the Champions League next season. The club may be prepared to allow his contract to run down and take the hit on losing him for a minimal sum in 2015.

The difficulty persuading world-class players to drop to Europa League football means they are unlikely to replace Rooney with a better player next summer, if they fail to make the Champions League.

Gary Neville does not believe Mata fits in with the “typical philosophy” of United — but feels the player would bring plenty of positives if he did make the move.